Liquid crystal display device achieving imaging with high s/n ratio using invisible light

Abstract

A liquid crystal panel brightness controller notifies a backlight controller that an illuminance of ambient light is equal to or less than a threshold value. Upon notification, the backlight controller causes invisible light emitted, for example. The invisible light passes through a liquid crystal panel and is reflected by an imaging target and is received by photosensors. Accordingly, the decrease in the amount of the visible light received by photosensors is compensated. As a result, an image with a high S / N ratio is obtained.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2006-172562 filed Jun. 22, 2006; the entire contents of which are incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a liquid crystal display device achieving imaging with a high S / N ratio using an invisible light source in addition to a visible light source.[0004]2. Description of the Related Art[0005]A liquid crystal display device has an array substrate in which signal lines, scanning lines, thin film transistors (TFT) and the like are formed. The device also has a driving circuit for driving the signal lines and the scanning lines.[0006]Recently, as the technology in integrated circuit has been developed, TFTs and a driving circuit can be formed in an array substrate by polysilicon process.[0007]This makes a liquid crystal device be miniaturized. And the d...

AI Technical Summary

Benefits of technology

[0020]According to the first aspect of the present invention, the invisible light passes through the liquid crystal panel and is reflected by the imaging target and is received by the photosensors, thus, total amount of received light can be larger than total amount of light to be received in the case the invisible light source is not used. As a result, an image with a high S / N ratio can be obtained even if brightness of the liquid crystal panel is decreased.

[0021]In the device, the visible light source controller means controls the intensity of the visible light in case the illuminance of the ambient light is decreased, and the invisible light source controller means controls the intensity of the invisible light not necessary in case the illuminance of the ambient light is high. It is possible to control the intensity of the visible light and the invisible light precisely. As a result, reducing power consumption can be done.

[0024]In the second aspect of the present invention, a peak of wavelength of the invisible light is equal to or more than 760 nm, and equal to or less than 1000 nm. Accordingly, the device is prevented from adversely affecting eyes.

Problems solved by technology

In case the brightness of the liquid crystal panel is decreased so as to reduce the amount of glare, or in case that an image which makes the brightness decreased is displayed, it becomes difficult to obtain an image with a high S / N ratio.

And it becomes likely that misdetection in the touch-detection happens.

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